全文获取类型
收费全文 | 205528篇 |
免费 | 15619篇 |
国内免费 | 7804篇 |
专业分类
电工技术 | 11241篇 |
技术理论 | 14篇 |
综合类 | 11215篇 |
化学工业 | 35696篇 |
金属工艺 | 10541篇 |
机械仪表 | 12004篇 |
建筑科学 | 16408篇 |
矿业工程 | 4943篇 |
能源动力 | 5849篇 |
轻工业 | 12686篇 |
水利工程 | 3211篇 |
石油天然气 | 11072篇 |
武器工业 | 1345篇 |
无线电 | 25483篇 |
一般工业技术 | 26708篇 |
冶金工业 | 10935篇 |
原子能技术 | 2114篇 |
自动化技术 | 27486篇 |
出版年
2024年 | 881篇 |
2023年 | 3264篇 |
2022年 | 5831篇 |
2021年 | 7908篇 |
2020年 | 5795篇 |
2019年 | 5009篇 |
2018年 | 5414篇 |
2017年 | 6200篇 |
2016年 | 5692篇 |
2015年 | 7291篇 |
2014年 | 9520篇 |
2013年 | 12275篇 |
2012年 | 12230篇 |
2011年 | 13871篇 |
2010年 | 11613篇 |
2009年 | 11466篇 |
2008年 | 10876篇 |
2007年 | 10468篇 |
2006年 | 10862篇 |
2005年 | 9633篇 |
2004年 | 6565篇 |
2003年 | 5781篇 |
2002年 | 5255篇 |
2001年 | 4723篇 |
2000年 | 4870篇 |
1999年 | 5639篇 |
1998年 | 5283篇 |
1997年 | 4351篇 |
1996年 | 3957篇 |
1995年 | 3313篇 |
1994年 | 2768篇 |
1993年 | 2188篇 |
1992年 | 1702篇 |
1991年 | 1277篇 |
1990年 | 1018篇 |
1989年 | 877篇 |
1988年 | 682篇 |
1987年 | 496篇 |
1986年 | 394篇 |
1985年 | 334篇 |
1984年 | 212篇 |
1983年 | 198篇 |
1982年 | 163篇 |
1981年 | 145篇 |
1980年 | 131篇 |
1979年 | 97篇 |
1978年 | 63篇 |
1977年 | 63篇 |
1976年 | 77篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 2 毫秒
991.
992.
993.
Relationship between mutagenic activity of drinking water and incidence of liver cancer was studied in Fusui County with micronucleus technique in the root tips of vicia faba. Results showed there existed substance that caused chromosome aberration in the drinking pond water of Fusui County. Micronucleus effects on the root tips of vicia faba induced by the substance in different kinds of drinking water coincided with the incidence of liver cancer (r = 0.86, P < 0.05). It suggested the existence of these chemical mutants in the water may be one of the important factors that caused high incidence of liver cancer. It provided experimental evidence for the etiological theory of liver cancer caused by the pollution of drinking water. 相似文献
994.
N Yamada MJ Emond RP Mills MM Leen PP Chen DC Stanford 《Canadian Metallurgical Quarterly》1998,7(6):378-387
Before use of cardiovascular surgical techniques and procedures in humans, many experiments, e.g., hypothermic circulatory arrest and cardiopulmonary bypass using the heart-lung machine, have been performed in the dog. As a consequence experimental canine cardiovascular surgery is highly developed. This has not resulted in the routine performance of open heart surgery in veterinary medicine, probably because of the high costs. Cardiovascular surgery in the dog is generally limited to interventions not depending on hypothermic circulatory arrest or cardiopulmonary bypass. The clinical cardiovascular surgery in dogs can be divided into routine and more specialized interventions. The first category includes correction of peritoneopericardial diaphragmatic hernia, pericardial fenestration in dogs with pericardial effusion, treatment of persistent right aortic arch, and patent ductus closure. The specialized interventions include dilation of pulmonic and aortic stenoses and pacemaker implantation. The diagnosis and surgical treatment of such diseases is described. New developments in cardiovascular surgical treatment that can be expected include catheter techniques for occlusion of shunts and dilations using balloons, because the financial costs of these procedures are not prohibitive. 相似文献
995.
We established an in vitro model of the phagocytosis of Mycobacterium tuberculosis by human peripheral blood monocytes to evaluate the subsequent inhibition of intracellular replication of the organism. Highly purified T cells (94% CD3(+)/CD16(-)) or natural killer (NK) cells (96% CD16(+)/CD3(-)) isolated by Percoll discontinuous density gradient of peripheral blood mononuclear cells were incubated with M. tuberculosis-infected monocyte monolayers. Monocytes were lysed immediately and at 4, 7, and 10 d after infection for quantification of intracellular replication, which was assessed by quantitative plating techniques as colony-forming units (CFU). Whereas control monocytes permitted intracellular replication, T cells activated monocytes to kill 77% (p < 0.01) of intracellular M. tuberculosis compared with control monocytes by 10 d after infection. NK cells activated monocytes to kill 84% (p < 0.01) of M. tuberculosis in comparison with control monocytes. Lymphokine (IL-2)-activated-killer (LAK) cells were capable of activating monocytes to kill 97% (p < 0.01) of the intracellular organisms compared with control monocytes. In purified protein derivative (PPD)-positive donors, PPD-specific-CD4(+) lymphocytes stimulated monocytes to kill intracellular M. tuberculosis in a Class II major histocompatibility complex-restricted manner. In contrast, in PPD-negative donors, CD4(-) lymphocytes activated monocytes in a genetically unrestricted manner. Both T cell supernatant and NK cell supernatant generated from cocultivation with M. tuberculosis-infected monocytes also activated monocytes to augment mycobactericidal function. In conclusion, T cells, NK cells, LAK cells, and their supernatants activated mycobactericidal function of monocytes, although these pathways of activation differed in terms of antigenic specificity and genetic restriction. 相似文献
996.
陶瓷模用α半水石膏的研究 总被引:1,自引:0,他引:1
理论上提出了影响陶瓷模用半水石膏常,高温性能的主要因素,即结晶形态.标准稠水度,初凝时间,抗折强度,进行了实验验证,确定了相应的制作技术,获得了性能优良的陶瓷模用α半水石膏。 相似文献
997.
Ding-Kai Chen Pen-Chung Yew 《Parallel and Distributed Systems, IEEE Transactions on》1996,7(5):463-476
It is extremely difficult to parallelize DOACROSS loops with nonuniform loop-carried dependences. In this paper, we present a static scheduling scheme with an accompanying synchronization strategy that can execute such DOACROSS loops effectively and efficiently. Our approach uses one of the parallelization techniques called Dependence Uniformization, which finds a small set of uniform dependence vectors to cover all possible nonuniform dependences in a DOACROSS loop. It differs from the previous schemes in that we demonstrate a better way to select the uniform dependence vectors. When used with the Static Strip Scheduling scheme, the proposed uniform dependence vector set allows us to enforce dependences with more locality, which reduces the requirement of explicit synchronization considerably while retaining most of the parallelism. This paper describes the uniform dependence vectors selection strategy and the static strip scheduling scheme. The performance analysis and examples are also presented 相似文献
998.
999.
Zhang Q. Brown D.A. Kung H. Townsend J.E. Chen M. Reinhart L.J. Morse T.F. 《Electronics letters》1995,31(6):480-482
The authors present a technique for detecting Bragg wavelength shifts using highly overcoupled couplers (HOCC). An HOCC of 60%/nm was fabricated with 626 cycles. With our HOCC, a 5 μW LED and a 95% reflective Bragg grating we were able to detect 10 μstrain (Δλ=0.01 nm) 相似文献
1000.
介绍了刚玉质狭缝型透气砖在30tVOD精炼炉中的应用,使用表明,该透气砖使用寿命长,供气特性好,综合效益显著。 相似文献